Whoever said that was probably thinking of the gas-impingement systems, which necessarily have some connection between the receiver and the gas port on the barrel (unlike direct-blowback systems). Whether that connection counts as negating a free float of the barrel depends on how you define "free-floating". It's certainly possible to have the handguard on such a gun not touch the barrel, which is how I expect most people would understand the term.

Free floating a bolt rifle simply means making sure there's no forearm touching the barrel, right? Why could that not be accomplished on a semi-automatic rifle? For example, a 10/22?

Maybe the comment was talking about an AR? Would that have something to do with the gas system?

As I understand "free float" it is that there is nothing connecting to the barrel what so ever. This would be different from just "free floated handguard" which could obviously be achieved on anything.

There some semi-auto's that cannot be free floated. M1/M1A/M14 or FAL being the classic example as the gas piston has to be in contact with both the action and the barrel. Technically I guess the AR cannot be free floated because the gas tube still connects the action to the barrel, but it is really negligible.

Obviously, anything that is strictly recoil or delayed blow back (1022, G3, etc.) can rather easily be free floated.

I suspect the dude was talking out his fourth point of contact. While it's true the AR has the gas system, it is still effectively free floated for a variety of complicated reasons, there are plenty of other semi-auto rifles out there that are completely and unquestionably free floated.

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Shoot, you can almost free-float an AK at this point. TWS current front handguard unit only grabs the barrel right in front of the receiver and has its own gas tube that doesn't actually contact the gas block.

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